1. Field of the Invention
The present invention relates to a method of manufacturing integrated circuits and other electronic devices. More particularly, the invention relats to an improved process for photoresist patterning in the manufacturing of integrated circuits and other electronic devices.
2. Description of the Related Art
The manufacture of integrated circutis requires an accurate and precise method to form patterns on wafers to delineate the areas for subsequent doping, isolation, and/or internal interconnection. The technology involved in the generation of these patterns is known as microlithography and it involves the following steps: (a) a mask or reticle is made with the required information, (b) a thin layer of a photosensitive polymer known as photoresist is coated onto the wafer, (c) the photoresist is exposed through the mask using the appropriate ultraviolet radiation, and (d) a relief image is formed using a suitable solvent called the developer.
The subsequent steps: etching, doping or deposition are carried out under vacuum. If as many as possible of the lithography steps could also be carried under vacuum, the level of particle contamination could be reduced. In the past the development of photoresist patterns in a dry environment has required the deposition of several film layers, such as: a top imaging layer, an intermediate layer to be used as a mask, and a bottom planarizing layer. This scheme, however, increases process complexity and is one of the main reasons why dry-development of photoresists has found no use in volume production of semiconductor devices. In addition of that, dry development of photoresists offers several advantages over conventional photoresist processing, among others less sensitivity to the rflectivity and topography of the underlying substrate.
Surface-sensitive processes,where only the surface of the resist needs to be exposed offer the performance advantages of multilayer schemes with the simplicity of single layer processing. The best known such processes is the so-called "DESIRE" process. This process consists in selectively incorporating silicon-containing species in the exposed areas of the photoresist from the gas phase using a silylating agent such as hexamethyldisilazane amine, HMDS. In an oxygen plasma, the regions that have incorporated silicon turn into silicon dioxide. This protects the underlying photoresist from the oxygen plasma whereas the unexposed regions are etched away in the plasma, with the end result that a relieve image is formed.
If the silylation, the dry-develop, the subsequent substrate etch and resist removal could be performed sequentially in the same chamber, in separate chambers with of the same piece of equipment, in separate chambers with vacuum wafer transfer, lower particle contamination could be achieved. This in turn would improve the yield,and increase throughput. Furthermore, in low volume production of application specific devices, higher equipment utilization can be achieved reducing initial capital requirements.